Renin is a proteolytic enzyme produced and secreted into the bloodstream by the juxtaglomerular cells of the kidney. In the bloodstream, renin cleaves a peptide bond in the serum protein angiotensinogen to produce a decapeptide known as angiotensin I. A second enzyme known as angiotensin converting enzyme, cleaves angiotensin I to produce the octapeptide known as angiotensin II. Angiotensin II is a potent pressor agent responsible for vasoconstriction and elevation of cardiovascular pressure. Attempts have been made to control hypertension by blocking the action of renin or by blocking the formation of angiotensin II in the body with inhibitors of angiotensin I converting enzyme.
Classes of compounds published as inhibitors of the action of renin on angiotensinogen include renin antibodies, pepstatin and its analogs, phospholipids, angiotensinogen analogs, pro-renin related analogs and peptide aldehydes.
A peptide isolated from actinomyces has been reported as an inhibitor of aspartyl proteases such as pepsin, cathepsin D and renin [Umezawa et al, in J. Antibiot. (Tokyo), 23:259-262 (1970)]. This peptide, known as pepstatin, was found to reduce blood pressure in vivo after the injection of hog renin into nephrectomized rats [Gross et al, Science, 175, 656 (1971)]. Pepstatin has the disadvantages of low solubility and of inhibiting acid proteases in addition to renin. Modified pepstatins have been synthesized in an attempt to increase the specificity for human renin over other physiologically important enzymes. While some degree of specificity has been achieved, this approach has led to rather high molecular weight hepta- and octapeptides [Boger, et al, Nature, 303, 81 (1983)]; high molecular weight peptides are generally considered undesirable as drugs because gastrointestinal absorption is impaired and plasma stability is compromised.
Short peptide aldehydes have been reported as renin inhibitors [Kokubu et al, Biochem. Biophys. Res. Common., 118, 929 (1984); Castro et al, FEBS Lett., 167, 273 (1984)]. Such compounds have a reactive C-terminal aldehyde group and would likely be unstable in vivo.
Other peptidyl compounds have been described as renin inhibitors. EP Appl. #128,762, published Dec. 18, 1984, describes dipeptide and tripeptide glycol-containing compounds as renin inhibitors [also see Hanson et al, Biochem, Biophys. Res. Comm., 132:155-161 (1985), 146:959-963 (1987)]. EP Appl. #181,110, published May 14, 1986, describes dipeptide histidine derivatives as renin inhibitors. EP Appl. #189,203, published Jul. 30, 1986, describes peptidylaminodiols as renin inhibitors. EP Appl. #200,406, published Dec. 10, 1986, describes alkyl naphthylmethyl propionyl-histidyl aminohydroxy alkanoates as renin inhibitors.
For other articles describing previous efforts to devise renin inhibitors, see Marshall, Federation Proc., 35: 2494-2501 (1976); Burton et al, Proc. Natl. Acad. Sci. USA, 77: 5476-5479 (1980); Suketa et al, Biochemistry, 14: 3188 (1975;) Swales, Pharmac. Ther., 7: 173-201 (1979); Kokubu et al, Nature, 217: 456-457 (1986); Matsushita et al, J. Antibiotics, 28: 1016-1018 (1975); Lazar et al, Biochem. Pharma., 23:2776-2778 (1974); Miller et al., Biochem, Pharma., 21:2941-2944 (1972); Haber, Clinical Science, 59: 7s-19s (1980); Rich et al, J. Org. Chem., 43: 3624 (1978); J. Med. Chem., 25: 27 (1980); especially Haber, Clin. and Exper. Hyper., A5(7&8), 1193 (1983); and European Patent Applications 172346A and 172347A published Feb. 26, 1986.